There is well known a control apparatus for a vehicle provided with a motor/generator functioning as a drive power source, and a step-variable transmission which constitutes a part of a power transmitting path between the drive power source and drive wheels and which is placed in a selected one of a plurality of gear or speed positions with an engagement of a selected one or ones of a plurality of coupling devices. A hybrid vehicle disclosed in JP-2014-223888A is an example of this type of vehicle. This document discloses a control apparatus configured to control an output torque of the drive power source (a torque of a second motor/generator described in the document) during a shifting action of the step-variable transmission, on the basis of a required vehicle drive torque (required drive torque described in the document) corresponding to an operation amount of an accelerator pedal, such that an angular acceleration value (angular acceleration value of the second motor/generator described in the document) representing a state of a rotary motion of an input rotary member of the step-variable transmission coincides with a target value.
By the way, the vehicle provided with the motor/generator functioning as the drive power source can be braked with a regenerative braking force based on a regenerative torque (a negative torque) generated by the motor/generator, so that the required vehicle drive torque may have a negative value when the accelerator pedal is turned off, namely, returned back to its non-operated or fully released position. When the accelerator pedal is returned to its non-operated position in the process of a shift-up action of the step-variable transmission which is performed by placement of the accelerator pedal in an operated position, for instance, the output torque of the drive power source is reduced according to a decrease of the required vehicle drive torque, so that an input torque of the step-variable transmission is reduced. In this case, there is a risk of generation of a shifting shock of the step-variable transmission due to a loss of balance between the input torque of the step-variable transmission and a torque capacity of its coupling devices.